1. Field of the Invention
This invention generally relates to a LED lamp and its driving apparatus, and in more particular, relates to a LED lamp miniaturizing component size and providing isolation effect, and its driving apparatus.
2. Description of the Related Art
General lighting has an enormous effect in human activities and product property. Conventional general lighting includes incandescent lamp, fluorescent lamp and so on.
Since Edison improved the incandescent lamp in 1879, the incandescent lamp has been providing the low-price and convenient lighting source all the time. However, the incandescent lamp has drawbacks of low lighting efficiency, high power consumption, short life-time, heat-generating, and being easily broken. Particularly, global warming is a critical issue these days, and those drawbacks of the incandescent lamp are becoming more and more concerned by people. The fluorescent lamp is also the main device for providing indoor luminescence, and, however, still has problems of mercury contamination and high-voltage driven radiation.
The blue light LED based on GaN (Gallium Nitride) series blue light LED technology proposed by Nichia Corp., Japan, in 1996, excites YAG (yttrium aluminum garnet) phosphors to generate yellow fluorescence mixed with blue light to produce white light (blue light LED with YAG phosphors), and, therefore, the LEDs are henceforth stepping into the luminescence market.
The white light LED compared with the conventional incandescent lamp and fluorescent lamp has lots of advantages such as small physical size (lots of combinations), low heat-generating (reduced heat radiation), low power consumption (low voltage/current-initiated), long lifetime (more than 100,000 hours), quick response time (high frequency operation), environmental protection (enduring vibration, enduring impact without being broken, recyclable, and pollution-free), flat package, and being easily developed for light weight and small size products.
As the luminescence of the LED is improved and the LED cost downs is achieved, usages of the LED increases thereupon. Due to that the LED need to be D.C. voltage driven, if the LED wants to be applied to utility input (85Vac-264Vac) voltage usage, the corresponding driven circuits are essential.
FIG. 1 schematically illustrates a conventional LED drive circuit, wherein utility input voltage (85Vac-264Vac) is rectified and filtered into D.C. voltage to drive a resister being serially connected with several serial LEDs. For the LED drive circuit, the number of the several serial LEDs increases as many as possible to decrease the voltage drop and resistor power consumption between both ends of the resistor. However, in the LED drive circuit, as the voltage of utility input voltage slightly changes, the current through the serial LEDs would be affected and the luminescence is altered.
FIG. 2 schematically illustrates another conventional LED drive circuit, wherein utility input voltage (85Vac-264Vac) passes through a drive IC to provide a drive method of high voltage and steady current.
The LEDs for lamps are high power LEDs, and, frequently, the LEDs should be flatly mounted on a metal lamp cup of each lamp for heat dissipation. In the two above said conventional LED drive circuits, serial LEDs are directly connected with high voltage, and if the LEDs are still flatly mounted on the metal lamp cup of each lamp for heat dissipation, users might carelessly touch the metal lamp cup and thus directly electrically contact with the high voltage via the metal lamp cup.
FIG. 3 schematically illustrates still another conventional LED drive circuit, wherein the utility input voltage (85Vac-264Vac) is bucked via a front-end adapter to drive a drive IC to provide power for the serial LEDs. Even though the LEDs are still flatly mounted on the metal lamp cup of each lamp for heat dissipation, users would not electrically contact with the high voltage even carelessly touch the metal lamp cup. However, in this LED drive circuit, the front-end adapter could not be easily integrated and located into each lamp according to its size, and, as a result, the application and heat dissipation of this LED drive circuit are restricted.